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Potential for the transmission of foot-and-mouth disease virus from African buffalo (Syncerus caffer) to cattle
Research in Veterinary Science /986, 40, 278-280
Potential for the transmission of foot-and-mouth disease virus from African buffalo (Syncerus caffer) to cattle E. C. ANDERSON, Animal Virus Research Institute, Pirbright, Woking, Surrey GU24 ONF
Foot-and-mouth disease viruses of types SAT I and SAT 2 isolated from diseased cattle and carrier buffalo, either on the same farm or in the same ecological area within a short time of each other, were compared by T. oligonucleotide mapping. No similarity was observed between the maps obtained, indicating that the different populations of virus were unique to each species and that no interspecies transmission had occurred. FREE-LIVING African buffalo (Syncerus coffer) have been shown to maintain the virus of foot-and-mouth disease (fMD) independent of the disease in other species and are true maintenance hosts of the disease in Africa (Hedger 1981).
Buffalo are numerous and widespread in many countries in Africa but convincing epidemiological evidence of transmission of FMD to cattle is difficult to obtain because of the high incidence of the disease in cattle. Consequently, attempts to determine the importance of virus carrier buffalo have been confined to rather artificial circumstances where carrier buffalo have been kept either in close proximity to susceptible cattle in open pens (Condy and Hedger 1974) or in enclosed isolation units (Anderson et al 1979). In the former experiment, contact was maintained over two and a half years and, in the latter experiment, contact was maintained over periods of up to five months. In neither case was it possible to demonstrate transmission.
W623
W553
•
-. ...,•
•
-
.-•.
•
",
. -.-,,-.
•
W820
FIG 1: Comparison of SAT 1 viruses isolated from buffalo and cattle. Buffalo isolates: W553 11974).W623 (1976), W820 11981). Cattle isolate: 25/80 119801
278
279
Foot-and-mouth disease transmission
-
R1215
• _
•• ...
. ~
.
.......
.
..-
J-- .
.~-~:.= ••.. . -~
W622
21/61
• .~
;
~
. -- --
W819
•
~.:.
_:
FIG 2: Comparison of SAT2 viruses isolated from buffalo and cattle. Buffalo isolates: W622 (1976), We19 (1981), Cattle isolates: R1215 119761, 21/81 (1981)
More recently there have been two reports of the successful transmission of the disease from buffalo to cattle. In the first case, transmission of type SAT 3 virus occurred from carrier buffalo to susceptible zebu cattle which were kept in close proximity for two years, during which time no transmission occurred. The buffalo were then transported some 70 miles and returned three weeks later, following which the disease appeared in the in-contact cattle (Hedger and Condy 1985). In another experiment, Thomson et al (1985) demonstrated the transmission of SAT 2 virus from clinically infected buffalo to susceptible cattle kept in close contact in open-air pens. In normal circumstances close contact between buffalo and cattle does not occur, though both species frequently share the same range and water source. Furthermore, clinical disease and the concomitant excretion of large amounts of virus is unusual in buffalo and has only been reported in the Kruger National Park. With the ability now to compare FMD viruses biochemically, it is possible to obtain epidemiological data on transmission in the natural state. Virus isolates made from clinically infected cattle or convalescent carrier animals were compared by T) ribonuclease oligonucleotide mapping (La Torre et al 1982) with viruses isolated at the same time from buffalo in the same area. Although the T 1 map represents only about 5 per cent of the RNA genome, such maps have been shown to be reproducible and able to confirm the
identity and give an appreciation of genomic relatedness between virus isolates. In Fig I the SAT I strain 25/80 isolated from clinically infected cattle is compared with strain W820 isolated from a buffalo on the same farm one year later. Two earlier buffalo isolates W553 (1974) and W623 (1976) are included for comparison. While there is a similarity, but not identity, between the buffalo viruses they are quite different from the cattle isolate. Fig 2 shows the comparison of SAT 2 viruses. Strain RI215 was from a carrier bovine in 1976 and W622 from a buffalo in the same place in 1976. Strain 21/81 was from a clinical case in a Friesian cow in January 1981 and strain W819 was isolated from a buffalo in the same area in May 1981. There is no similarity between any of the viruses. Mutation frequencies in RNA viruses are extremely high and have been estimated at 10- J to 10- 4 at given base positions per replication (Holland et aI1982). However, not all mutants will establish themselves and, in a study of the evolution of FMD strains in a country where it is endemic, using T, mapping, Anderson et al (1985) showed that viruses isolated in the same ecological area within a few years of each other have similar T 1 maps. Viruses isolated during the course of the same outbreak showed few, if any, changes in their T) maps. It seems reasonable, therefore, to conclude from the present study that different virus populations were cycling in the two species, and that no interspecies transmission had
280
E. C. Anderson
occurred. Although further application of biochemical methods to compare viruses from the two species in their natural ecological situation is required, these data support the widely held belief that transmission of FMD between buffalo and cattle is not a common event.
References ANDERSON, E. C, DOUGHTY, W. J. & PALING, R. (1979) Journal of Comparative Pathology 89,541-549 ANDERSON, E. C, UNDERWOOD, B. o.. BROWN, F. & NGICHABE, C K. (1985) Veterinary Microbiology 10, 409-423 CaNDY, J. B. & HEDGER, R. S. (1974) Research in Veterinary Science 16, 182 HEDGER, R. S. (1981) Infectious Diseases of Wild Animals. Eds
J. W. Davis, L. H. Karstad and D. O. Trainer. Ames, Iowa State University Press. p 87 HEDGER, R. S. & CaNDY, J. B. (1985) Veterinary Record 117, 205 HOLLAND, J., SPINDLER, K., HORODYSKI, F., GRABAU, E., NICHOL, S. & VANDEPOL, S. (1982) Science 215,1577 LA TORRE, J. L., UNDERWOOD, B. o.. LEBENDIKER, M., GORMAN, B. M. & BROWN, F. (1982) Injection and Immunity 36,142 THOMSON, G. R., ESTERHUYSEN, J. J., GAINARU, M. D., BRUCE, W. & BENGIN, R. C (1985) Veterinary Viral Diseases - Their Significance in South-east Asia and the Western Pacific. Ed A. J. Della-Porta. New York, Academic Press. pp 298-301
Received for publication October 22, 1985 Accepted December 9, 1985
Potential for the transmission of foot-and-mouth disease virus from African buffalo (Syncerus caffer) to cattle E. C. ANDERSON, Animal Virus Research Institute, Pirbright, Woking, Surrey GU24 ONF
Foot-and-mouth disease viruses of types SAT I and SAT 2 isolated from diseased cattle and carrier buffalo, either on the same farm or in the same ecological area within a short time of each other, were compared by T. oligonucleotide mapping. No similarity was observed between the maps obtained, indicating that the different populations of virus were unique to each species and that no interspecies transmission had occurred. FREE-LIVING African buffalo (Syncerus coffer) have been shown to maintain the virus of foot-and-mouth disease (fMD) independent of the disease in other species and are true maintenance hosts of the disease in Africa (Hedger 1981).
Buffalo are numerous and widespread in many countries in Africa but convincing epidemiological evidence of transmission of FMD to cattle is difficult to obtain because of the high incidence of the disease in cattle. Consequently, attempts to determine the importance of virus carrier buffalo have been confined to rather artificial circumstances where carrier buffalo have been kept either in close proximity to susceptible cattle in open pens (Condy and Hedger 1974) or in enclosed isolation units (Anderson et al 1979). In the former experiment, contact was maintained over two and a half years and, in the latter experiment, contact was maintained over periods of up to five months. In neither case was it possible to demonstrate transmission.
W623
W553
•
-. ...,•
•
-
.-•.
•
",
. -.-,,-.
•
W820
FIG 1: Comparison of SAT 1 viruses isolated from buffalo and cattle. Buffalo isolates: W553 11974).W623 (1976), W820 11981). Cattle isolate: 25/80 119801
278
279
Foot-and-mouth disease transmission
-
R1215
• _
•• ...
. ~
.
.......
.
..-
J-- .
.~-~:.= ••.. . -~
W622
21/61
• .~
;
~
. -- --
W819
•
~.:.
_:
FIG 2: Comparison of SAT2 viruses isolated from buffalo and cattle. Buffalo isolates: W622 (1976), We19 (1981), Cattle isolates: R1215 119761, 21/81 (1981)
More recently there have been two reports of the successful transmission of the disease from buffalo to cattle. In the first case, transmission of type SAT 3 virus occurred from carrier buffalo to susceptible zebu cattle which were kept in close proximity for two years, during which time no transmission occurred. The buffalo were then transported some 70 miles and returned three weeks later, following which the disease appeared in the in-contact cattle (Hedger and Condy 1985). In another experiment, Thomson et al (1985) demonstrated the transmission of SAT 2 virus from clinically infected buffalo to susceptible cattle kept in close contact in open-air pens. In normal circumstances close contact between buffalo and cattle does not occur, though both species frequently share the same range and water source. Furthermore, clinical disease and the concomitant excretion of large amounts of virus is unusual in buffalo and has only been reported in the Kruger National Park. With the ability now to compare FMD viruses biochemically, it is possible to obtain epidemiological data on transmission in the natural state. Virus isolates made from clinically infected cattle or convalescent carrier animals were compared by T) ribonuclease oligonucleotide mapping (La Torre et al 1982) with viruses isolated at the same time from buffalo in the same area. Although the T 1 map represents only about 5 per cent of the RNA genome, such maps have been shown to be reproducible and able to confirm the
identity and give an appreciation of genomic relatedness between virus isolates. In Fig I the SAT I strain 25/80 isolated from clinically infected cattle is compared with strain W820 isolated from a buffalo on the same farm one year later. Two earlier buffalo isolates W553 (1974) and W623 (1976) are included for comparison. While there is a similarity, but not identity, between the buffalo viruses they are quite different from the cattle isolate. Fig 2 shows the comparison of SAT 2 viruses. Strain RI215 was from a carrier bovine in 1976 and W622 from a buffalo in the same place in 1976. Strain 21/81 was from a clinical case in a Friesian cow in January 1981 and strain W819 was isolated from a buffalo in the same area in May 1981. There is no similarity between any of the viruses. Mutation frequencies in RNA viruses are extremely high and have been estimated at 10- J to 10- 4 at given base positions per replication (Holland et aI1982). However, not all mutants will establish themselves and, in a study of the evolution of FMD strains in a country where it is endemic, using T, mapping, Anderson et al (1985) showed that viruses isolated in the same ecological area within a few years of each other have similar T 1 maps. Viruses isolated during the course of the same outbreak showed few, if any, changes in their T) maps. It seems reasonable, therefore, to conclude from the present study that different virus populations were cycling in the two species, and that no interspecies transmission had
280
E. C. Anderson
occurred. Although further application of biochemical methods to compare viruses from the two species in their natural ecological situation is required, these data support the widely held belief that transmission of FMD between buffalo and cattle is not a common event.
References ANDERSON, E. C, DOUGHTY, W. J. & PALING, R. (1979) Journal of Comparative Pathology 89,541-549 ANDERSON, E. C, UNDERWOOD, B. o.. BROWN, F. & NGICHABE, C K. (1985) Veterinary Microbiology 10, 409-423 CaNDY, J. B. & HEDGER, R. S. (1974) Research in Veterinary Science 16, 182 HEDGER, R. S. (1981) Infectious Diseases of Wild Animals. Eds
J. W. Davis, L. H. Karstad and D. O. Trainer. Ames, Iowa State University Press. p 87 HEDGER, R. S. & CaNDY, J. B. (1985) Veterinary Record 117, 205 HOLLAND, J., SPINDLER, K., HORODYSKI, F., GRABAU, E., NICHOL, S. & VANDEPOL, S. (1982) Science 215,1577 LA TORRE, J. L., UNDERWOOD, B. o.. LEBENDIKER, M., GORMAN, B. M. & BROWN, F. (1982) Injection and Immunity 36,142 THOMSON, G. R., ESTERHUYSEN, J. J., GAINARU, M. D., BRUCE, W. & BENGIN, R. C (1985) Veterinary Viral Diseases - Their Significance in South-east Asia and the Western Pacific. Ed A. J. Della-Porta. New York, Academic Press. pp 298-301
Received for publication October 22, 1985 Accepted December 9, 1985